A polymer composition comprising (per cent by weight): a) 70-84% of a crystalline propylene polymer having an amount of isotactic pentads (mmmm), measured by 13C-MNR on the fraction insoluble in xylene at 25° C., higher than 97.5 molar %; b) 8-15% of an elastomeric copolymer of ethylene and propylene, the copolymer having an amount of recurring units deriving from ethylene ranging from 25 to 50 wt % and being partially soluble in xylene at ambient temperature; the polymer fraction soluble in xylene at ambient temperature having an intrinsic viscosity value ranging from 2.5 to 3.5 dl/g; and c) 8-15% of ethylene homopolymer having an intrinsic viscosity value ranging from 1.5 to 4 dl/g; said composition having a value of melt flow rate ranging from 55 to 90 g/10 min, and the amount of hexane extractables lower than 3.5 wt %.